Oscillation generator



Jan. 3, 1928.

C A. SPRAGUE OSCILLATIQI I GENERATOR Filed Jan. 15. 1922 2 Sheets-Sheet l 3:2 whom QEQ space current through the tube.

Patented Jan. 3, 1928.

UNITED, STATES PATENT OFFICE.

CLARENCE.A. SPRAGUE, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 013' vNEW YOBK,:N. Y., A COBFORATION 0F NEVJ' YORK.

OSCILLATION GENERATOR.

Application filed January 13, 1922. Serial ,No. 528,905;

This inventionrelates to generators of electric oscillations and more particularly to generators 1n which continuous oscllla- ,tions are produced by periodically applying an electric impulse to a resonant cir'a cuit.

electric oscillations at high, efficiency.

In accordance with the present invention electric oscillations are generated by a vacuum tube amplifier type. A highly negative polarizing potential on the grid of the tube tends toprevent the flow of any substantial amount of A complex control wave having a component of fundamental frequency and a component of three times the fundamental frequency in proper phase relation is impressed upon the grid to suddenly render the tube highly conductive to space current and then suddenly return the tube to its original nonconducting condition. In this manner direct current from, the space current source is elliciently converted into alternating current. A tuned circuit resonant to waves of fundamental frequency is coupled to the output.

circuit of the amplifier to select the wave of desired frequency therefrom.

Instead of employing-a single tube, two tubes may be used arranged as abalanced amplifier and having the space current normally/blocked by a highly negative grid potential. scribed above is impressed upon thegrids of the amplifier. In this case an impulse is produced alternately in the output circuit of one of said tubes and then in theoutput circuit of the other tube, thus providing two impulses for each cycle ofthe fundamental wave. The amplitude of theoscillations set up in the tuned circuit coupled to the balanced amplifier outputcircuit is maintained more constant than the amplitude of oscillations set up in a tuned circuitby only a single impulse during each cycle. On account of the generated wave being replenished with" energy twice during each cycle, the ratio of fundamental to harmonic wave energy in a circuit containing a load is greater than in the case where only a single impulse occurs during each cycle. By providing one or more feedback One object of the invention is to generate 7 I view ofthe appended drawing and claims.

of the space current.

The complex control wave de,

circuits between the input and output-circuits of a balanced amplifier, oscillations may be generated in accordance with this invention by regenerative action.

Other objects of the'invention will be apparent from the more detailed description of the invention which follows taken in Fig. 1 is a circuit diagram illustrating a simple form of the invention employing a single amplifier tube to generate oscillations; Fig. Qis a graph illustrating the wave form of the complex control wave applied to the grid of the amplifier; Fig. 3 is a circuit diagram illustrating an oscillation generator employing abalanced amplifier; Fig. 4 is acircuit diagram of a. bal

anced amplifier'provided with a feed-back circuit to generate oscillations by regenerative action; Fig. 5, which is similar to Fig. 4L, shows a circuit diagram in which two feed-back circuits are provided.

Referring to Fig. '1, the source of electric ond harmonic 'frequency" 3fi having a fre quency three times that of the fundamental frequency. The device 3 I known type of distorting device j which is adapted to operate in responseto an impressed wave to distortsaid wave and produce a second harmonic tl'iereof. These fundamental and harmonic waves, combined in the form of a complex'control wave, are transmitted through the inductive coupling or transformer 4 to the input circuit 5 of the amplifier tube 6 of the well-known space current type having a source of polarizing E. M. F. 7 in the input circuit 5t0 apply a high negative potential to the grid 8 to prevent the fiow of any substantial amount of space current from the source 9 in the output a circuit 10.

Variations of current or impulsesin the output c1rcu1t 10 are transmitted by means of'an inductive coupling or transformer 11 to'the tunedcircuit 12 including the induc tance 13 and the capacity-14c as well as inductance andv capacity effectively in said cirmay be any wellcuit by virtue of the coupling 11, the connected load or other associated circuits which may be coupled with the circuit 12. The'cir cuit 12 is adjusted to be of minimum impedance to the wave of fundamental frequency f Resistance 15 represents the load through which the waves in the circuit 12 pass. The sourceof space current 9 is preferably made large in order to provide a large flow of current during the brief period when space curv rent flows through the output circuit 10.

In Fig.2, the ordinates represent grid potentials while abscissze represent intervals of time. Curve illustrates the wave of fundamental frequency and corresponds to the component of fundamental frequency transmitted from the harmonic producer 3 to the grid 8 or it may represent the wave transmitted from source 1 of the harmonic producer lVave 21 of three times the fundamental frequency is transmitted from the harmonic producer 3 simultaneously with the wave 20 and is in such phase relation with respect to the wave 20 that a maximum or crest in the wave 20 occurs simultaneously with a maximum or crest of like sign occurring in the wave 21, thereby producing a resultant wave 22 having a series of sharp peaks 23 remote from the zero axis of the wave. The Zero axisof the waves corresponds to the 'E. M. F. of the polarizing source 7.

The polarizing E. M. F. 7 is made so large that no substantial amount of space current can flow through the output circuit 10 until the grid potential, varying in accordance with the Wave 22, is in excess of that indicated by the dotted line 24. It will thus be seen that on the rising slope of the wave the amplifier 6 suddenly becomes conducting,

v being a maximum at the point 23 and then suddenly returns to a non-conducting condition on the downward slope of the wave up- "on reaching the pointcorresponding to the dotted line 24-, this process occurring once during each cycle of the fundamental wave 20.

' Wave 22 is made of such intensity that the potential corresponding to the point 23 produces a minimum impedance through the tube 6. As a result of the rapid change in conductivity of the tube 6 from'zero to a maximum, and vice versa, or in other words,

of the variationin resistance from a maxi mum to a minimum, and vice versa, the loss of energy in the tube 6 is reduced to a minimum, the period of time during which the loss in thetube is large being negligible, or

very small, depending upon whether the rate ofchange of grid potential is, respectively, more or less abrupt.

Fig. 3 shows a source of complex control 'waves 30 to transmit waves offundamental frequency f, and of second harmonic frequency 3, through the inductive coupling grids 32, 33.

current begins to n the source 39, while dotted line 25rep- "through the tube 3-1 34, arranged as a balanced amplifier having an input circuit 36 and an output circuit 37. The source of polarizing potential 38 maintains grids 32 and 33 at such a high negative potential as to prevent the flow of any substantial amount of space current from the source 39. The windings of trans former 31 are so poled as to apply components of potentials of opposite sign to Navies set up in output circuit 37 are transmitted by means of the transformer or inductive coupling to the tuned circuit 411 which contains the inductance 12 andvariable capacity 43, together with the inductance .sistance id represents the resistance of the load to which the waves flowing through the circuit 11 are subjected. 1

The complex wave from the source 30 has approximately the same shape as curve 22, Fig. The zero axis of the waves in this case corresponds to the E. M. F .of the polarizing source 38. During the first half cycle of wave 20, the wave 22 eontainsthe neal"23which is applied as an impulse of iivepotential to the grid 32,-an1dis then renewed inthe succeeding half cycle of wave 20, by a second peak 23 which is applied, as an impulse of positive potential to the grid 2 Similarly, a positive peat: is applied' to first grid 32 and then grid33, during each cycle of'the fundamental wave 20;

The dotted line 2 lrepresents the critical potential of the grid 32 above which space flow through the tube 34 resents the critical 'potential of the grid 33 which is of such value that potentials'more removed from the zero axis of the wave than the dotted line 25 produce space current through the'tube 35 from the source 39. It will thus be seen that during one half eycle of the wave 20, space current rapidly builds the tube until the tube becomes of.

up 111 minimum impedance, the current being then suddenly reduced to zero. During the succceding'half cycle of the wave 20, space current builds upsuddenlyin the t ube35 and then is suddenly reduced to zero." similar flow of space current occurs'in the tubes 3% and 35 during subsequent cycles;

The windings of the transf men 40 are so poled that a space current impulse produces an opposite effect in the work circuit at]. from that pro? duced by a. space current impulse through the tube During each 'cyclethere are therefore produced two impulses through purpose of adjusting I fundamental wave with respect to thatof tenuates the fundamental the output circuit 37 and the work cirquency which are stored up by resonance in the work or load c1rcu1t41. Inasmuch as energy is supplied to the circuit'41 twice during each cycle, the current flowing through the resistance 44 is maintained'more constant than would be the case if one of the impulses were omitted, for example, as in work circuit 12, Fig. 1. The source 80 may-consist of the elements 1, 2, 3, shown in Fig. 4 shows an oscillator operating ina manner similar to that of the circuit shown in Fig. 3. In this case, space current impulses transmitted alternately through the tubes 84 and 35 transformer 40 to the work circuit 50 which is adjusted to resonance with the fundamental frequency by means of the capacity 51.

of fundamental fre- In addition to waves quency, setup in the work circuit 50, waves of harmonic frequency are also produced, among these being waves of second harmonic frequency.

-' The variable resistance 52 is provided to adjust the phase relation between the fundamental and second harmonic waves, these Waves being transmitted by means of the transformer 53'through the feed-back circuit 54 and through the transformer 31 to the input circuit 36.

Feed-back circuit 54 contains the tuned, or anti-resonant circuit 55 adjusted approximately to resonance with the wave of fundamental frequency by ductance 56 and variable capacity-'57 for the the amplitude of'the the second harmonic wave.

of the fundamental wave in the feed-back circuit 54 is increasedby detuning the circuit 55 and decreased by tuning circuit 55 more closely to resonance with the fundamental wave. -Capacity 58 permits of adjusting the. capacity r-eactance of the circuit 54 inductive reactance at the second harmonic frequency, thus providing a low impedance to the second harmonic Wave.

' In general, the feed-back circuit 54 atwave transmitted to the input circuit36 relatively more than the second harmonic wave in order to provide thedesired relative amplitudes for The amplitude these waves, the relatively greater attenuation of the fundamental Wave being due to the higher impedance of the circuit to this wave. 7 r g Variable resistance 59 is providedto cou trol the phaserelation between the fundamental and second harmonic waves as well as controlling the amplitudes of these waves.

are supplied through the 'clusion of other waves in means of variable in-- to be equal to that of the p which may be so chosen harmonic wave is adjusted to. the proper "phase relationship with respect to the funcuit 36, or in other words,

'waves20 and21 in Fig. 2. Vance 72 permits of ad usting the second Waves of fundamental frequency besides having the relation shown in Fig. 2 to waves ofsecond harmonic frequency are adjusted by means of either or both of the phaseadjusting resistances 52and 59 so that the control'wave 22 transmitted through the feedback circuit 54 and impressed upon the tubes 34 and 35 produces a flow ofspace current which generates a wave in ready set up therein. In. other words, the time occurring between two successive positive peaks impressed upon the grid of the tube 34 is made, exactly equal to that of the period ofthe fundamental wave 20.

Work circuit 50 includes the transformer 60 which transmits Waves to the filter 61 designed to pass wavof desired frequency, such as the fundamental waves, to the exthe circuit 50. A load to be supplied with the desired waves such as those of fundamental frequency, may be connected to the terminals 62. Filter 61 may be designed in accordance with the'disclosure in linited States patent, to G- A. Campbell No. 1,227,113.

Fig. 5 is similar to Fig. 4, but shows two feed-back circuits 65 and 66 in place of the single feed-back circuit 54 in Fig. 4. Vork circuit 50 is coupled to feed-back circuits 65 and 66 by means of transformer 67 .while feed-back circuits 65 and 66 are coupled to the input circuit of the balanced amplifier 34, 35 by means Feed-back circuit 65. is designed to transmit waves of fundamental frequency and contains the filter, network, or tuned circuit69 designed to pass waves of fundamental frequency and. suppress waves quencies.

In the case where the element 69 is a filter circuit, a sufficient number of sections may be: provided to adjust the'phase of the fundamental wave component to be impressed upon the input circuit36 so that the waves impressedupon the. input circuit 36 willfbe in proper phase relation'to the waves already set up in the work circuit .50. Resistance .70 ermits. of adjusting the amplitude of the fundamentalwave to the desired value.

Feed-back circuit 661s designedto transmit a wave component (if-second harmonic frequency and contains the filter network or tuned circuit 71 designed to pass waves of second harmonic. frequency and suppress waves of other frequencies. Element 71 conof' other frethe work circuit 50in exact synchronismwith the wave. al-

of the transformer 68.;

sistsof afilter, the number of sections of I that the second damental wave transmitted to-the input cirto provide the approximate relationship indicated between Variable resistharmonic wave to the desired amplitude. Filters 69 and 71 may be constructed similarly to filter 61, Fig. 4. The term balanced amplifier. as used-in the specification and claimsis intended to designate an amplifier of the space discharge type having two space current paths and control elements therefor connected in opposite sense with respect to the potentials applied thereto.

Many variations may be made in the specific arrangements of the above circuits and in the methods of operating them without departing from the broad features of the invention disclosed.

Features of the invention believed to be novel are pointed out in the appended claims.

'What is claimed is a '1. In a generator of amplifier of the space current type having two-spacecurrentpaths and control elements therefor connected in opposite sense with'respect to the potential applied thereto, input and output circuits for said amplifier, means associated with said input circuit to normally prevent transmission of any sub stantial amount of space. current through said output circuit, a source of waves having a component of fundamental frequency and various components 'harmonically related thereto associated with said input circuit, means for causing the crests-of certain of said components to occur at the same time to cause space current to be transmitted alternately through one and then the other of said paths, and a work circuit associated with said amplifier output circuit' 2. In a generator of electric. waves, an ampllfier having two space current paths and control elements therefor connected in opposite sense with respect to the potential applied thereto, an input and an output circuittherefor, a source of waves having a component of fundamental frequency and of three timesthe fundamental frequency cou- 'pled to 'said input circuit, means for causing the crests'of said components to occur at the same time, means associated with said input circuit to prevent the transmission of any substantial amount of space current through said amplifier during a portion of each cycle of said fundamental wave, and a work circuit associated with said amplifier output circuit.

8. In an amplifier havingtwo space current paths and control elements therefor connected in opposite sense with respect to the potential applied thereto, an input and an output ,circuit therefor, the method of generating oscillations in said output circuit which "comprises impressing a polarizing potentialupon said input circuit to normal- 1y prevent the transmission of any substantial amount of space current through said output circuit, and applying to said input electric waves, an

applied thereto,

circuit-a wave comprising a component of fundamental frequency and-various components harmonicallyrelated thereto the crests of which occur at the same time. to

an output circuit therefor, the method of.

generating oscillations in said output circuit which comprises impressing acpolarizing potential upon said input circuit to normally prevent the transmission of any substantial amount of space current through said-output circuitand impressing a wave comprising a component of fundament'alfrequency and a secondharmonic component of the fundamental frequency, the crests of one of said components occurring at the "same time as the crests of the fundamental'to produce sudden impulses in said outputcircuit. 5. in. a generator 0f-electr1c waves, an

amplifier having input and output circuits, awork circuit associated with said output circuit, and, coupled between said wo'rk and input circuits, a single feed-back circuit resonant'to awave of harmonic frequency and containing a circuit quency for adjusting the; relative amplitudes of the fundamental and harmonic frequency Waves. I

6. In a generator of electric waves, an amplifier having two space current paths and control elements therefor connected in opposite sense with respect to thejpotential applied thereto, input and output circuits therefor, icuitsto feed back a peaked wave comprising a wave of fundamental frequency and various components harmonically related thereto having their'crests occurring. at the same time from said output tosaid input circuit. V I I 7. In a generator of *electric waves, an amplifier having two space current'paths and control elements therefor COIlIlBCiCl'ill opposite sense with respect toth-e potential input and output circuits therefore, a tuned work circuit associated with said output circuit, and means coupled between said workand input circuit tofeed back a peaked wave comprising a wave of fundamental frequency and various components harmonically related thereto and having their crests occurring at the same times as those of the fundamental wave from said work circuit to said input circuit.

8. In a generator of electric waves,.a-n amplifier having input and output circuits, and means coupled between said circuits to food back a plurality of Wave frequencies from said output circuit to said input-cirsubstantially anti resonant to a wave of fundamental fre and means associated with said circuit and to adjust the time of occurrence of crests in one of said waves to coincide with the crests in another of said waves.

9. In a generator of electric waves, an amplifier having input a single feedback circuit coupled between said output and input circuits to transmit a plurality of wave frequencies between said v output and input circuits, and means in said feed-back circuit to adjust the relative amplitudes of the waves transmitted therethrough.

11. In a generator of electric waves, an amplifier having input and output a single feed-back circuit coupled between said output and input circuits to transmita plurality of wave frequencies between sai output and input circuits, and phase shifting and amplitude controlling means in said feed-back circuit. 1

12. The method of producing oscillations whichcomprises producing a complex wa veconsisting of components of fundamental and second harmonic frequency in such phase relation that each crest in said fundamental wave occurs at substantially the same time as a crest of like sign in said harmonic wave, said crests forming peaks in said complex wave, amplifying only that portion of each peak which is remote from the zero axis of said complex wave whereby a complex output wave is generated, and

and output circuits,

circuits,

selecting a wave of fundamental frequency from said output wave.

13. The method of producing oscillations which comprises producing a complex wave consistin of components of fundamental and harmonic frequency in such phase relation that each crest in said fundamental wave occurs at substantially the same time as a crest of like signin said harmonic wave, said crests forming peaks in said complex wave, amplifying portions of said complex wave lying on oppositesides of the zero axis of said complex wave whereby a complex output wave is generated, and selecting a wave of fundamental frequency from said output wave. 7

14. In a genera-torof electric waves, an amplifier having input and output circuits, associated with said output circuit a tune work circuit, in which wave components of fundamental frequency and harmonically related thereto are produced, including means for controlling the relative phases of said components to produce a peaked wave,

and means coupled between said work cird cuit and said input circuit to feed back said peaked wave.

15. In a generator of electric waves, an

amplifier cuit, a single feed-back circuit coupling said outputand input circuits to rality of wave frequencies therebet-Ween, said feed-back circuit being resonant to one of said frequencies and including a circuit substantially anti-resonant to another of said frequencies.

In witness whereof, I hereunto subscribemy name this 11th day of January, A. D. 1922; v 4

CLARENCE A. SPRAGUE,

having an input and output cirtransmit a plu- 

